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Meningitis | 마이메르시 MyMerci
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Meningitis

NCLEX Review Guide: Meningitis

Pathophysiology

Definition and Etiology

  • Meningitis is an inflammation of the meninges, the protective membranes covering the brain and spinal cord. The inflammation can be caused by bacteria, viruses, fungi, parasites, or non-infectious factors.
  • Bacterial meningitis is most commonly caused by Streptococcus pneumoniae, Neisseria meningitidis, and Haemophilus influenzae type B, with the latter being less common due to vaccination.
  • Viral meningitis (aseptic meningitis) is most commonly caused by enteroviruses, herpes simplex virus, and arboviruses, and generally has a more benign course than bacterial meningitis.

Key Points

  • Bacterial meningitis is a medical emergency requiring immediate antibiotic treatment.
  • Meningococcal meningitis (caused by N. meningitidis) can cause rapidly progressive disease and is associated with outbreaks.

Pathophysiological Process

  • Pathogens typically enter the subarachnoid space through hematogenous spread (bloodstream), direct invasion (from sinusitis, otitis media, skull fractures), or via neural pathways.
  • Once in the subarachnoid space, pathogens trigger an inflammatory response, increasing blood-brain barrier permeability and causing cerebral edema, increased intracranial pressure, and potential cerebral hypoperfusion.

Key Points

  • The inflammatory cascade in meningitis can lead to neuronal damage, cerebral edema, and increased intracranial pressure.
  • Complications include seizures, hydrocephalus, cerebral infarction, and cranial nerve palsies.

Clinical Manifestations

Classic Triad and Common Symptoms

  • The classic triad of meningitis includes fever, nuchal rigidity (stiff neck), and altered mental status, though all three may not be present in every patient.
  • Other common symptoms include severe headache, photophobia (sensitivity to light), phonophobia (sensitivity to sound), nausea, vomiting, and irritability.
  • Infants may present with nonspecific symptoms such as poor feeding, irritability, lethargy, and a bulging fontanelle rather than the classic triad.

Clinical Scenario

A 20-year-old college student presents to the emergency department with a 12-hour history of severe headache, fever (39.5°C), and neck stiffness. The patient reports photophobia and has vomited twice. On examination, positive Kernig's and Brudzinski's signs are noted. These findings strongly suggest meningitis, requiring immediate lumbar puncture and empiric antibiotic therapy.

Key Points

  • Kernig's sign (resistance to passive knee extension when hip is flexed) and Brudzinski's sign (involuntary hip and knee flexion when neck is flexed) indicate meningeal irritation.
  • Rash, particularly a petechial or purpuric rash, may indicate meningococcal meningitis and is a critical finding requiring immediate intervention.

Differences in Presentation by Age

  • Neonates may present with temperature instability (hypothermia or hyperthermia), poor feeding, irritability, lethargy, seizures, and a bulging fontanelle.
  • Elderly patients often present with atypical symptoms such as confusion, altered mental status, and absence of fever, making diagnosis challenging.

Key Points

  • The classic triad of meningitis is present in only about 44-66% of cases, so absence does not rule out diagnosis.
  • Immunocompromised patients may have minimal symptoms despite severe infection.

Diagnosis

Diagnostic Procedures

  • Lumbar puncture (LP) is the gold standard for diagnosis, allowing analysis of cerebrospinal fluid (CSF) for cell count, glucose, protein, culture, and other tests.
  • Blood cultures should be obtained before antibiotic administration, as they may identify the causative organism in 50-80% of bacterial meningitis cases.

CSF Findings in Different Types of Meningitis

Parameter Normal Bacterial Viral Fungal/TB
Appearance Clear, colorless Cloudy, turbid Clear to slightly cloudy Clear to cloudy
WBC count 0-5 cells/mm³ 1,000-5,000+ cells/mm³ (neutrophils) 50-1,000 cells/mm³ (lymphocytes) 50-500 cells/mm³ (lymphocytes)
Protein 15-45 mg/dL Elevated (>100 mg/dL) Mildly elevated (50-100 mg/dL) Elevated (>100 mg/dL)
Glucose 45-80 mg/dL (2/3 of serum) Decreased (<40 mg/dL) Normal or slightly decreased Decreased

Key Points

  • Neuroimaging (CT/MRI) should be performed before LP if there are signs of increased intracranial pressure or focal neurological deficits to avoid herniation.
  • Antibiotic therapy should not be delayed for diagnostic procedures in suspected bacterial meningitis.

Additional Diagnostic Tests

  • PCR testing of CSF can rapidly detect bacterial and viral pathogens, especially valuable when patients have received antibiotics before LP.
  • Serum procalcitonin and C-reactive protein levels may help distinguish bacterial from viral meningitis when CSF results are ambiguous.

Key Points

  • CSF lactate >35 mg/dL strongly suggests bacterial meningitis.
  • Gram stain of CSF has a sensitivity of 60-90% for bacterial meningitis and can guide initial antibiotic therapy.

Treatment and Nursing Management

Antibiotic Therapy

  • Empiric antibiotic therapy should be initiated immediately after obtaining blood cultures and preferably before LP in suspected bacterial meningitis.
  • Common empiric regimens include a third-generation cephalosporin (ceftriaxone or cefotaxime) plus vancomycin, with ampicillin added for neonates, elderly, and immunocompromised patients to cover Listeria monocytogenes.

Important Alert

Never delay antibiotic administration in suspected bacterial meningitis. Each hour of delay in antibiotic administration increases mortality risk. If lumbar puncture will be delayed, administer antibiotics immediately after obtaining blood cultures.

Key Points

  • Antibiotic therapy is typically continued for 7-14 days for bacterial meningitis, depending on the causative organism.
  • Dexamethasone (corticosteroid) may be administered before or with the first dose of antibiotics to reduce inflammation and improve outcomes in certain types of bacterial meningitis, particularly pneumococcal meningitis.

Nursing Care

  1. Perform thorough neurological assessments every 2-4 hours to monitor for changes in level of consciousness, pupillary responses, and development of focal deficits.
  2. Administer prescribed medications including antibiotics, antipyretics, analgesics, and anticonvulsants as ordered.
  3. Monitor vital signs, including temperature, closely. Implement cooling measures for hyperthermia as this can worsen neurological outcomes.
  4. Maintain fluid and electrolyte balance while monitoring for signs of SIADH (Syndrome of Inappropriate Antidiuretic Hormone secretion), a common complication.
  5. Implement seizure precautions and be prepared to administer anticonvulsants if seizures occur.
  6. Monitor for signs of increased intracranial pressure (decreasing level of consciousness, pupillary changes, bradycardia, hypertension, irregular respirations).
  7. Provide a quiet, dimly lit environment to reduce sensory stimulation for patients with photophobia and phonophobia.
  8. Implement infection control measures, including droplet precautions for suspected or confirmed meningococcal meningitis.

Memory Aid: MENINGITIS Assessment

  • Mental status changes
  • Elevated temperature
  • Nuchal rigidity (stiff neck)
  • Increased intracranial pressure signs
  • Nausea and vomiting
  • Gait abnormalities
  • Irritability
  • Tremors or seizures
  • Intolerance to light and sound
  • Skin rash (especially with meningococcal)

Key Points

  • Isolation precautions are necessary for the first 24 hours of antibiotic therapy in bacterial meningitis, with droplet precautions specifically for meningococcal meningitis.
  • Identify and notify close contacts of patients with meningococcal meningitis, as they may require prophylactic antibiotics.

Complications and Prevention

Potential Complications

  • Acute complications include seizures, increased intracranial pressure, cerebral edema, hydrocephalus, cerebral infarction, cranial nerve palsies, and shock.
  • Long-term sequelae may include hearing loss, cognitive impairment, motor deficits, seizure disorders, and learning disabilities, particularly in children.

Key Points

  • Sensorineural hearing loss occurs in approximately 10% of patients with bacterial meningitis, particularly with pneumococcal meningitis.
  • The mortality rate for untreated bacterial meningitis approaches 100%, while even with treatment, mortality ranges from 5-30% depending on the causative organism and timing of intervention.

Prevention Strategies

  • Vaccination is the primary preventive measure, with vaccines available against common bacterial causes including Haemophilus influenzae type B, Streptococcus pneumoniae, and Neisseria meningitidis.
  • Chemoprophylaxis with antibiotics (typically rifampin, ciprofloxacin, or ceftriaxone) is recommended for close contacts of patients with meningococcal meningitis.

Key Points

  • The meningococcal vaccine is recommended for adolescents, college freshmen living in dormitories, military recruits, and individuals with certain medical conditions.
  • Healthcare workers exposed to patients with meningitis should follow standard precautions and may require prophylaxis if exposed to respiratory secretions from patients with meningococcal meningitis.

Summary of Key Points

  • Meningitis is an inflammation of the meninges, most commonly caused by bacterial, viral, or fungal pathogens.
  • The classic triad includes fever, nuchal rigidity, and altered mental status, though not all may be present.
  • Lumbar puncture with CSF analysis is the gold standard for diagnosis, with characteristic findings differentiating bacterial, viral, and fungal causes.
  • Bacterial meningitis is a medical emergency requiring immediate empiric antibiotic therapy, typically with a third-generation cephalosporin plus vancomycin.
  • Nursing care focuses on neurological assessment, medication administration, monitoring for complications, and infection control.
  • Complications include acute neurological issues and long-term sequelae such as hearing loss and cognitive impairment.
  • Prevention strategies include vaccination and chemoprophylaxis for close contacts in meningococcal cases.

Quick Check

Which of the following CSF findings would be most consistent with bacterial meningitis?

  1. Clear CSF with 100 WBC/mm³ (predominantly lymphocytes), normal glucose, slightly elevated protein
  2. Cloudy CSF with 2,000 WBC/mm³ (predominantly neutrophils), decreased glucose, elevated protein
  3. Clear CSF with 300 WBC/mm³ (predominantly lymphocytes), decreased glucose, markedly elevated protein
  4. Bloody CSF with 500 WBC/mm³ (mixed), normal glucose, elevated protein

Answer: B - Cloudy CSF with 2,000 WBC/mm³ (predominantly neutrophils), decreased glucose, elevated protein is classic for bacterial meningitis.

Commonly Confused Points

Bacterial vs. Viral Meningitis

Feature Bacterial Meningitis Viral Meningitis
Onset Rapid (hours to days) Gradual (days)
Severity Severe, life-threatening Usually mild, self-limiting
CSF appearance Cloudy, turbid Clear to slightly cloudy
CSF WBC 1,000-5,000+ cells/mm³ (neutrophils) 50-1,000 cells/mm³ (lymphocytes)
CSF glucose Decreased (<40 mg/dL) Normal or slightly decreased
Treatment Immediate IV antibiotics Supportive care, antivirals for specific causes
Prognosis High mortality and morbidity without treatment Usually complete recovery

Common Pitfalls

  • Assuming meningitis is not present if the classic triad is absent - only about 44-66% of patients present with all three symptoms.
  • Delaying antibiotic administration until after diagnostic procedures - antibiotics should be given immediately after blood cultures in suspected bacterial meningitis.
  • Failing to implement appropriate isolation precautions - droplet precautions are essential for meningococcal meningitis.
  • Overlooking the need for prophylaxis for close contacts in meningococcal cases.
  • Confusing viral and bacterial meningitis based on symptoms alone - CSF analysis is essential for differentiation.

Study Tips

Memory Aid: "MENINGITIS" Treatment Priorities

  • Monitor neurological status frequently
  • Empiric antibiotics immediately
  • Notify contacts for prophylaxis (meningococcal)
  • Isolation as appropriate
  • Nutrition and hydration management
  • Glucose monitoring (CSF and serum)
  • ICP monitoring and management
  • Temperature control
  • Implementation of seizure precautions
  • Supportive care (pain, light/sound sensitivity)

Memory Aid: CSF Findings "WPG" Pattern

For bacterial meningitis, remember "↑↑↓" (pronounced "up-up-down"):

  • WBCs: ↑↑ (Markedly increased, neutrophil predominant)
  • Protein: ↑↑ (Markedly increased)
  • Glucose: ↓ (Decreased)

For viral meningitis, remember "↑→→" (pronounced "up-normal-normal"):

  • WBCs: ↑ (Mildly increased, lymphocyte predominant)
  • Protein: → to ↑ (Normal to mildly increased)
  • Glucose: → (Normal)

Study Checklist

  • Review pathophysiology of meningitis
  • Memorize the classic triad and variations by age
  • Learn CSF findings for different types of meningitis
  • Understand empiric antibiotic therapy regimens
  • Review nursing care priorities and neurological assessment
  • Know complications and prevention strategies
  • Understand isolation requirements and prophylaxis indications
  • Practice NCLEX-style questions on meningitis

Remember, early recognition and prompt treatment of meningitis can be life-saving. Focus on understanding the pathophysiology, recognizing the clinical presentation, and knowing the immediate nursing interventions. You've got this!

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